Chemistry · 2015 · May · Paper 2 · HL · TZ1 · Question paper

24EP01 [Personal identifier removed] Chemistry Higher level Paper 2 © International Baccalaureate Organization 2015 24 pages 2215 – 6108 Instructions to candidates  Write your session number in the boxes above.  Do not open this examination paper until instructed to do so.  Section A: answer all questions.  Section B: answer two questions.  Write your answers in the boxes provided.  A calculator is required for this paper.  A clean copy of the chemistry data booklet is required for this paper.  The maximum mark for this examination paper is [90 marks]. 2 hours 15 minutes Thursday 14 May 2015 (afternoon) – 2 – Section A Answer all questions. Write your answers in the boxes provided. 1. Ethanedioic acid is a diprotic acid. A student determined the value of x in the formula of hydrated ethanedioic acid, HOOC−COOH•xH2O, by titrating a known mass of the acid with a 0.100 mol dm−3 solution of NaOH (aq). 0.795 g of ethanedioic acid was dissolved in distilled water and made up to a total volume of 250 cm3 in a volumetric flask. 25 cm3 of this ethanedioic acid solution was pipetted into a flask and titrated against aqueous sodium hydroxide using phenolphthalein as an indicator. The titration was then repeated twice to obtain the results below. Volume of 0.100 mol dm–3 NaOH / cm3 Titration 1 Titration 2 Titration 3 Final burette reading (± 0.05) 13.00 25.70 38.20 Initial burette reading (± 0.05) 0.00 13.00 25.70 Volume added (a) Calculate the average volume of NaOH added, in cm3, in titrations 2 and 3, and then calculate the amount, in mol, of NaOH added. [2] ..................................................................... ..................................................................... ..................................................................... ..................................................................... (This question continues on the following page) 24EP02 M15/4/CHEMI/HP2/ENG/TZ1/XX